150 
THE FOREST AS A SHELTER. 
consequence of the felling of the woods on the Apennines, the 
sirocco prevails greatly on the right hank of the Po, in the 
Parmesan territory, and in a part of Lombardy ; it injures the 
harvests and the vineyards, and sometimes ruins the crops of 
the season. To the same cause many ascribe the meteoro¬ 
logical changes in the precincts of Modena and of Peggio. In 
the communes of these districts, where formerly straw roofs 
resisted the force of the winds, tiles are now hardly sufficient; 
in others, where tiles answered for roofs, large slabs of stone 
are now ineffectual; and in many neighboring communes the 
grapes and the grain are swept off by the blasts of the south 
and southwest winds. 
On the other hand, according to the same authority, the 
pinery of Porto, near Kavenna—which is 33 kilometres long, 
and is one of the oldest pine woods in Italy—having been 
replanted with resinous trees after it was unfortunately cut, 
has relieved the city from the sirocco to which it had become 
exposed, and in a great degree restored its ancient climate.* 
The felling of the woods on the Atlantic coast of Jutland 
has exposed the soil not only to drifting sands, but to sharp 
sea winds, that have exerted a sensible deteriorating effect on 
the climate of that peninsula, which has no mountains to serve 
at once as a barrier to the force of the winds, and as a store¬ 
house of moisture received by precipitation or condensed from 
atmospheric vapors.f 
It is evident that the effect of the forest, as a mechanical 
impediment to the passage of the wind, would extend to a very 
considerable distance above its own height, and hence protect 
while standing, or lay open when felled, a much larger surface 
than might at first thought be supposed. The atmosphere, 
movable as are its particles, and light and elastic as are its 
masses, is nevertheless held together as a continuous whole by 
the law of attraction between its atoms, and, therefore, an ob¬ 
struction which mechanically impedes the movement of a given 
* Le Alpi die cingono VItalia, pp. 370, 371. 
t Bergsoe, Reventlovs Virlcsomhed, ii, p. 125. 
